A feasibility study of ECBM recovery and CO2 storage for a producing CBM field in Southeast Qinshui Basin, China

This paper presents a geo-engineering and economic analysis of the potential for enhanced coalbed methane (ECBM) recovery and CO2 storage in the South Shizhuang CBM Field, Southeast Qinshui Basin, China. We construct a static model using the well log and laboratory data and then upscale this model to use in dynamic simulations. We history match field water and gas rates using the dynamic model. The parameters varied during the history match include porosity and permeability. Using the history matched dynamic model, we make predictions of CBM and ECBM recoveries for various field developments. We build a techno-economic model that calculates the incremental nominal net present value (NPV) of the ECBM incremental recovery and CO2 storage over the CBM recovery. We analyse how the NPV is affected by well spacing, CH4 price, carbon credit and the type of coal. Our analyses suggest that 300 m is the optimum well spacing for the study area under the current CH4 price in China and with a zero carbon credit. Using this well spacing, we predict the recoveries for different injection gas compositions of CO2 and N-2 and different injection starting times. The results show that gas injection yields incremental CBM production whatever the composition of the injected gas. Pure CO2 injection yields highest ECBM for low swelling coals while flue gas injection gives highest ECBM for high swelling coals. However, the differences in recoveries are small. Injection can be economically viable depending on the CH4 price and the carbon credit. At current prices and no carbon credit, flue gas injection is commercial. At higher CH4 prices and/or with the introduction of carbon credits, co-optimisation could be commercially viable. High carbon credits favour injecting pure CO2 rather than other gases because this stores more CO2. Injecting CO2 at late stage increases CO2 storage but decreases the project's NPV. High-swelling coals require about $20/tonnes additional carbon credit. (C) 2013 Elsevier Ltd. All rights reserved.